Abstract: The invention relates to a solar water heating system which comprises: (a) a photovoltaic array for converting sun radiation to DC voltage; (b) a water tank which comprises a single heating element; and (c) a connection box receiving a first input from said photovoltaic array, and a second input from an AC residential supply, and outputting a combined voltage to said single heating element at the water tank, wherein said combined output voltage is a combination of one or more of—(i) a full rectified signal resulting from said AC residential supply passing through a full rectification semi-conductor element; and (ii) a DC voltage resulting from said DC voltage from the photo voltaic array passing through a unidirectional semi-conductor element.

Abstract: The invention relates to a method for heating water in a domestic water heating system that comprises the steps of: (a) providing a water tank containing mw liters of water; (b) providing at least one temperature sensing unit in said water tank for sensing the temperature of the water in the tank: (c) providing a heating element in said water tank; (d) providing a control unit for activating said heating element, said control unit continuously receiving indication for the water temperature from said temperature sensing unit; (e) providing to said control unit a desired water temperature, and designating a time for using the water at said desired temperature; (f) knowing the current water temperature, the desired water temperature at said designated time, the power of the heating element, and the specific heat of the water, calculating by the control unit the heating period ?t needed for heating the water in the tank from the current temperature as measured by said temperature sensing unit, to the desired temp

Abstract: The invention relates to a method for heating water in a domestic water heating system, that comprises the steps of: (a) providing a water tank containing mw liters of water, (b) providing at least one temperature sensing unit in said water tank for sensing the temperature of the water in the tank: (c) providing a heating element in said water tank; (d) providing a control unit for activating said heating element, said control unit continuously receiving indication for the water temperature from said temperature sensing unit; (e) providing to said control unit a desired water temperature, and designating a time for using the water at said desired temperature; (f) knowing the current water temperature, the desired water temperature at said designated time, the power of the heating element, and the specific heat of the water, calculating by the control unit the heating period &Dgr;t needed for heating the water in the tank from the current temperature as measured by said temperature sensing unit, to the desired